linux-kernel - Re: [PATCH v8 07/12] mm/hugetlb: Set the PageHWPoison to the raw error page

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Date:   Fri, 11 Dec 2020 14:36:29 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        paulmck@...nel.org, mchehab+huawei@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, rdunlap@...radead.org,
        oneukum@...e.com, anshuman.khandual@....com, jroedel@...e.de,
        almasrymina@...gle.com, rientjes@...gle.com, willy@...radead.org,
        mhocko@...e.com, song.bao.hua@...ilicon.com, david@...hat.com,
        duanxiongchun@...edance.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v8 07/12] mm/hugetlb: Set the PageHWPoison to the raw
 error page

On Thu, Dec 10, 2020 at 11:55:21AM +0800, Muchun Song wrote:
> +static inline void subpage_hwpoison_deliver(struct hstate *h, struct page *head)
> +{
> +	struct page *page = head;
> +
> +	if (!free_vmemmap_pages_per_hpage(h))
> +		return;
> +
> +	if (PageHWPoison(head))
> +		page = head + page_private(head + 4);
> +
> +	/*
> +	 * Move PageHWPoison flag from head page to the raw error page,
> +	 * which makes any subpages rather than the error page reusable.
> +	 */
> +	if (page != head) {
> +		SetPageHWPoison(page);
> +		ClearPageHWPoison(head);
> +	}
> +}

I would make the names coherent.
I am not definitely goot at names, but something like:
hwpoison_subpage_{foo,bar} looks better.

Also, could not subpage_hwpoison_deliver be rewritten like:

  static inline void subpage_hwpoison_deliver(struct hstate *h, struct page *head)
  {
       struct page *page;
  
       if (!PageHWPoison(head) || !free_vmemmap_pages_per_hpage(h))
               return;
  
       page = head + page_private(head + 4);
       /*
        * Move PageHWPoison flag from head page to the raw error page,
        * which makes any subpages rather than the error page reusable.
        */
       if (page != head) {
               SetPageHWPoison(page);
               ClearPageHWPoison(head);
       }
  }

I think it is better code-wise.

> +	 * Move PageHWPoison flag from head page to the raw error page,
> +	 * which makes any subpages rather than the error page reusable.
> +	 */
> +	if (page != head) {
> +		SetPageHWPoison(page);
> +		ClearPageHWPoison(head);
> +	}

I would put this in an else-if above:

	if (free_vmemmap_pages_per_hpage(h)) {
		set_page_private(head + 4, page - head);
	        return;
	} else if (page != head) {
		SetPageHWPoison(page);
		ClearPageHWPoison(head);
	}

or will we lose the optimization in case free_vmemmap_pages_per_hpage gets compiled out?


-- 
Oscar Salvador
SUSE L3